Hopefully you got the memo that gut health is a key component to overall health. The trillions of microorganisms living in your gut play a major role in everything from digestion to immunity to cognition — and can even impact your emotions. (Fun fact: A large amount of your serotonin is produced in the gut).

But did you know that certain strains of bacteria can actually influence your ability to shed unhealthy — unwanted — pounds? “When your microbiome is out of whack, it’s almost impossible to lose weight,” says Jordan Crofton, FNP, Director of Patient Care at THE WELL.

Research continues to demonstrate that the composition of gut bacteria in your system can either help or hinder your ability to move the needle on the scale. How do these microscopic germs have such sway?

In one recent study, researchers found that genes within these bacteria can influence the rate at which bacteria grows, the effectiveness of nutrient absorption from food and whether certain nutrients (like fiber and starches) get broken down into sugars in a way that can impact weight loss.

“We’ve identified specific genetic signatures in the gut microbiome that were predictive of weight loss response in a small cohort of patients following a healthy lifestyle intervention,” study author Sean Gibbons, PhD, 

“In our study, we found that some of the fastest-growing microbes in the weight-loss responder group were from the genus Prevotella,” says Gibbons.

On the flip side, Gibbons and his team also found some strains of bacteria are linked to weight loss resistance — specifically, the bacteria that produce an increase in enzymes needed to turn starches and fibers into sugar.

Crofton agrees, noting specific bacterial strains that can be particularly problematic:

“Two bacterial phyla called Bacteroidetes and Firmicutes dominate the human digestive tract, and analyses have found that high Firmicutes and low Bacteroidetes (resulting in a high F/B ratio) is a microbial imbalance that can lead to weight gain, inflammation and impaired insulin sensitivity,” explains Crofton.

“Research also shows us that there are decreased levels of Akkermansia muciniphila (one of the most abundant beneficial microbes in the human microbiome) in patients struggling with obesity and metabolic syndrome,” says Crofton, adding that these levels are one of the things she makes sure to evaluate for in her patients.